The present invention relates generally to communication, and more specifically to a hands-free speakerphone apparatus.
Hands-free speakerphone devices are commonly used for many applications such as speakerphone, hands-free car kit, teleconferencing system, cellular phone, hands-free voice recognition devices, and so on, and in various environments such as car, home, office, hotel, and so on. Hands-free speakerphone devices allow users to speak into microphones placed at some distance away from the users and to listen to sound via speakerphones also placed away from the users. Hands-free speakerphone devices are thus convenient and comfortable to use, and are also safer to use than hands-on or hand-held devices in certain situations, e.g., when driving a car. Hands-free speakerphone devices may also be designed for use with different communication channels such as, e.g., digital wireline channels (e.g., data/computer networks), analog channels (e.g., conventional telephone lines), wireless channels (e.g., cellular phones), and so on. As used herein, a communication channel is a means via which a hands-free speakerphone device exchanges signals with a remote or far-end device.
A hands-free speakerphone device typically includes a loudspeaker and one or more microphones. When the hands-free speakerphone device is small in size, the close proximity of the loudspeaker to the microphones can cause some major problems. For example, when a speech signal from a remote user is outputted from the loudspeaker, a portion of this speech signal may be reflected to the microphones and transmitted back to the remote user. This acoustic disturbance is referred to as echo. In general, users are annoyed by hearing their own voice delayed, for example, by the path of the system. In certain instances, acoustic shock or howling may be caused by the speakerphone device becoming unstable due to the microphones picking up reflections of the acoustic signal emitted by the loudspeaker.
Hands-free speakerphone devices are described in various literatures including U.S. Patent Application Serial Nos. US 2003/0086562 and US 2002/0183101. U.S. Patent Application Serial No. US 2003/0086562 describes using an anti-sealing feature for hands-free speakerphone to alleviate acoustic leakage. U.S. Patent Application Serial No. US 2002/0183101 describes using an attenuator to cancel acoustic feedback with cellular phone. However, the techniques described in these U.S. patent applications do not provide good performance for true hands-free full-duplex communications.
As can be seen, a hands-free speakerphone device that can effectively provide hands-free communication is highly desirable.